Investments in Joint Ventures (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018	Jun. 30, 2016	Oct. 04, 2006
Total Investment	$ 94,937		$ 94,937		$ 88,884
Total Assets of the Partnership	183,130		183,130		152,700
Net Loss of the Partnership			(893)		(149)
Company's share of Net Loss of the Partnership	(272)	$ (11)	(536)	$ (23)	(88)
Investments in real estate, net	162,956		162,956		116,859
Cash and cash equivalents	14,995		14,995		35,777
Deferred costs	5,093		5,093		64
Unrealized rents & receivable	86		86		0
Secured notes payable	23,380		23,380		9,549
Other liabilities	16,142		16,142		4,930
Capital - FRP	105,942		105,942		100,282
Capital - Third parties	37,666		37,666		37,939
Total liabilities and capital	$ 183,130		$ 183,130		$ 152,700
Brooksville Quarry, LLC
Ownership percent	50.00%		50.00%		50.00%		50.00%
Total Investment	$ 7,478		$ 7,478		$ 7,449
Total Assets of the Partnership	14,309		14,309		14,325
Net Loss of the Partnership			(44)		(122)
Company's share of Net Loss of the Partnership			(22)		(61)
Investments in real estate, net	14,296		14,296		14,299
Cash and cash equivalents	11		11		20
Deferred costs	2		2		6
Unrealized rents & receivable	0		0		0
Secured notes payable	0		0		0
Other liabilities	42		42		119
Capital - FRP	7,478		7,478		7,449
Capital - Third parties	6,789		6,789		6,757
Total liabilities and capital	$ 14,309		$ 14,309		$ 14,325
BC FRP Realty, LLC
Ownership percent	50.00%		50.00%		50.00%	50.00%
Total Investment	$ 5,652		$ 5,652		$ 5,976
Total Assets of the Partnership	22,425		22,425		21,371
Net Loss of the Partnership			(660)		0
Company's share of Net Loss of the Partnership			(330)		0
Investments in real estate, net	22,281		22,281		21,352
Cash and cash equivalents	17		17		11
Deferred costs	101		101		8
Unrealized rents & receivable	26		26		0
Secured notes payable	11,181		11,181		9,549
Other liabilities	50		50		38
Capital - FRP	5,597		5,597		5,892
Capital - Third parties	5,597		5,597		5,892
Total liabilities and capital	22,425		22,425		21,371
Hyde Park
Total Investment	859		859		594
Total Assets of the Partnership	859		859		594
Net Loss of the Partnership			0		39
Company's share of Net Loss of the Partnership			0		39
Investments in real estate, net	859		859		594
Cash and cash equivalents	0		0		0
Deferred costs	0		0		0
Unrealized rents & receivable	0		0		0
Secured notes payable	0		0		0
Other liabilities	0		0		0
Capital - FRP	859		859		594
Capital - Third parties	0		0		0
Total liabilities and capital	$ 859		$ 859		$ 594
RiverFront Holdings II, LLC
Ownership percent	80.00%		80.00%		80.00%
Total Investment	$ 25,453		$ 25,453		$ 19,865
Total Assets of the Partnership	65,957		65,957		38,869
Net Loss of the Partnership			(391)		(66)
Company's share of Net Loss of the Partnership			(386)		(66)
Investments in real estate, net	65,704		65,704		38,793
Cash and cash equivalents	253		253		76
Deferred costs	0		0		0
Unrealized rents & receivable	0		0		0
Secured notes payable	12,199		12,199		0
Other liabilities	11,313		11,313		1,887
Capital - FRP	36,814		36,814		31,347
Capital - Third parties	5,631		5,631		5,635
Total liabilities and capital	$ 65,957		$ 65,957		$ 38,869
Bryant Street Partnerships
Ownership percent	61.36%		61.36%		61.36%
Total Investment	$ 55,495		$ 55,495		$ 55,000
Total Assets of the Partnership	79,580		79,580		77,541
Net Loss of the Partnership			202		0
Company's share of Net Loss of the Partnership			202		0
Investments in real estate, net	59,816		59,816		41,821
Cash and cash equivalents	14,714		14,714		35,670
Deferred costs	4,990		4,990		50
Unrealized rents & receivable	60		60		0
Secured notes payable	0		0		0
Other liabilities	4,737		4,737		2,886
Capital - FRP	55,194		55,194		55,000
Capital - Third parties	19,649		19,649		19,655
Total liabilities and capital	$ 79,580		$ 79,580		$ 77,541